Katelyn Horne has been promoted to partner in Arnold & Porter’s International Arbitration Practice Group, effective January 2026. She represents clients in investor-state and commercial arbitration and has contributed to the firm’s exceptional record of success, including nine victories on behalf of sovereign clients over the past nine years. Katelyn also advises on public international law, with a focus on human rights, climate change, the law of the sea, and sovereign immunity. Katelyn previously served as an associate legal officer at the International Court of Justice and in the Executive Branch of the U.S. Government.